On August 25, the National Weather Service Grand Junction issued a forecast indicating that daily afternoon thunderstorms will occur throughout the week, primarily affecting the higher terrain of eastern Utah and western Colorado. These storms may bring frequent lightning, gusty winds, and localized heavy rainfall.
High pressure is moving into the Desert Southwest, contributing to a gradual warming trend. Daytime highs are expected to be 5 to 10 degrees above normal for late August and may continue to increase through Friday. While monsoonal moisture is shifting east, surface moisture will persist, with precipitable water values remaining between 100% and 150% of normal through the end of the week.
Localized heavy rainfall remains a threat for flash flooding, particularly over susceptible terrain and recent burn scars. If storms form over sensitive areas or train over the same location, flash flooding and debris flows are possible. Convective activity is expected to favor higher terrain, with primary aviation concerns including lightning, gusty outflow winds of approximately 25 kts, and brief periods of MVFR conditions due to heavy rain.
A potential pattern shift is expected late this week into the weekend as a deep trough approaches the West Coast. This could lead to stronger winds and localized Critical Fire Weather conditions, though current guidance is in poor agreement regarding whether the pattern will be wet or dry. If troughing overspreads the western United States through the weekend, it may introduce a cooler and wetter pattern with temperatures near a few degrees below normal heading into early September.
